The wireless device industry has recently seen unprecedented growth. With the growth of this industry, communication between wireless devices has become increasingly important. There are a number of different technologies for inter-device communications. Radio Frequency (RF) technology has been the predominant technology for wireless device communications. Alternatively, electro-optical devices have been used in wireless communications. Electro-optical technology suffers from low ranges and a strict need for line of sight. RF devices therefore provide significant advantages over electro-optical devices.
Conventional RF technology employs continuous sine waves that are transmitted with data embedded in the modulation of the sine waves' amplitude or frequency. For example, a conventional cellular phone must operate at a particular frequency band of a particular width in the total frequency spectrum. Specifically, in the United States, the Federal Communications Commission has allocated cellular phone communications in the 800 to 900 MHz band. Generally, cellular phone operators divide the allocated band into 25 MHz portions, with selected portions transmitting cellular phone signals, and other portions receiving cellular phone signals.
Another type of inter-device communication technology is ultra-wideband (UWB). UWB wireless technology is fundamentally different from conventional forms of RF technology. UWB employs a “carrier free” architecture, which does not require the use of high frequency carrier generation hardware; carrier modulation hardware; frequency and phase discrimination hardware or other devices employed in conventional frequency domain communication systems. UWB communications systems and devices additionally benefit from the capability to measure distance and geo-position. Generally, these UWB devices measure the time it takes for a UWB pulse, or signal to travel from one UWB device to another UWB device, and use the speed of light to determine the distance between UWB devices.
However, the broad concept of using time and the speed of light to determine distance has been employed for centuries. The first recorded attempts to establish the speed of light by the use of distance date back to the experiments of Galileo in the 1600s. His only conclusion based on his terrestrial experiments was that light moves very fast. In 1676, Olaf Roemer was able to measure the speed of light to be approximately 2.14×10 8 based on his assumptions of the distance between Jupiter and the Earth. The current accepted measurement of 2.9997924588×108 was obtained using laser interferometery.
In theory, a wireless ultra-wideband (UWB) communications pulse, or signal transmitted from a source and received by a target arrives without any delays or distortions caused by the surrounding environment. Such an ideal environment is difficult to realize outside the vacuum of outer space. In more practical environments and especially in urban settings, the environment may have a substantial impact on the reception of a UWB pulse, or signal.
Generally, the distance between communicating devices affects the quality of the communications channel. Electromagnetic radiation dissipates proportionally to distance squared. Additionally, the terrain affects radio waves. Thus, the opportunity for multi-path, or “fading” effects generally increases with distance. There are essentially two types of fading in electromagnetic communications. Local multi-path fluctuation is known as fast-fading or Raleigh fading. More distance fading effects may be caused by long term variation in average power levels, slow fading or log-normal fading, which is caused by movement over distances long enough to produce significant variations in the signal path length. Multi-path reflections can also cause a signal to arrive at the receiver in multiple reflections, each at a different time. This is commonly referred to as delay spread. As signal strength attenuates or decreases, the signal-to-noise ratio (SNR) degrades as well, generally leading to increased bit-error-rates (BER).
Therefore, there exists a need for an ultra-wideband communication system that provides reliable communication at a variety of distances, and in a variety of environments.